The present invention generally relates to seat belt retractors which include a means of absorbing or dissipating crash energy.
In a conventional seat belt retractor, a web or a vehicle (often called inertial) sensor is used to initiate the stoppage of the spool to prevent further protraction of the seat belt webbing therefrom during an accident. A second class of seat belt retractors permits the controlled protraction of the seat belt by incorporating within the retractor an energy absorption (or dissipation) mechanism. In the past these mechanisms have included crushable bushings (U.S. Pat. No. 5,547,143), deformable tubes (U.S. Pat. No. 3,881,667) or torsion bars (U.S. Pat. No. 3,741,494).
It is an object of the present invention to provide an energy absorbing retractor that has one or more load limiting levels, a retractor that may be activated either mechanically or electrically, and one which utilizes a unique energy absorbing (dissipating) mechanism.